Digital Video Broadcasting-Terrestrial (DVB-T) is a European-based transmission standard for digital terrestrial television and has generally allowed Europe and other countries to proceed with the digitalization of television broadcasting.
In 2006, standardization of Digital Video Broadcasting-Second Generation Terrestrial (DVB-T2) which is a transmission standard for the second generation terrestrial television was started to improve the frequency usage efficiency.
As with the DVB-T standard, the DVB-T2 standard also adopts the Orthogonal Frequency Division Multiplexing (OFDM) method (see Non Patent Literatures 1 and 2).
FIG. 1 is a diagram showing a transmission frame structure according to the DVB-T2 standard.
The DVB-T2 standard has a concept called a physical layer pipe (PLP). More specifically, as one of the characteristics of the DVB-T2 standard, transmission parameters such as a modulation method and a code rate, can be set independently for each PLP. The number of PLPs is 1 at the minimum and 255 at the maximum. FIG. 1 shows the case where the number of PLPs is 10, as an example.
The following is a transmission frame structure.
Super frame=N_T2 frames (N_T2=2 to 255)
Frame=P1 symbol+P2 symbols+data symbols
P1 symbol=1 symbol
P2 symbol=N_P2 symbols (N_P2 is uniquely identified by the FFT size)
Data symbol=L_data symbols (L_data is variable, having upper and lower limits)
The P1 symbol is 1 k in the FFT size and is sent using a guard interval (GI)=½. The P1 symbol includes 7 bits of information of S1 and S2 to transmit information, such as the FFT size, regarding the P2 symbol and the data symbol following the present P1 symbol.
The P2 symbol includes L1 signaling information in a first half and main signal data in a remaining second half. The data symbol includes the rest of the main signal data.
The L1 signaling information to be sent by the P2 symbol includes L1-pre information used mainly for transmitting information that is common to all the PLPs. Moreover, the L1 signaling information includes L1-post information used mainly for transmitting information that may be different for each of the PLPs.
FIG. 2 is a diagram showing a configuration of a transmitting apparatus 2000 according to the DVB-T2 standard (see Non Patent Literature 1 (the DVB-T2 specification)).
The transmitting apparatus 2000 includes two transport stream (TS) generation units 2010 and 2011 and a physical layer processing unit 2012.
It is shown, as an example, that the TS generation unit 2010 generates two programs in a TS.
To be more specific, the TS generation unit 2010 includes an audio coding unit (shown as 20211 and 20212) and a video coding unit (shown as 20221 and 20222) for each of the programs.
Moreover, the TS generation unit 2010 includes a packetization unit (shown as 20231 to 20234) for each of the audio and video service components in the corresponding program.
Furthermore, the TS generation unit 2010 includes a packetized-stream multiplexing unit 2024 and a layer-2 (L2) information processing unit 2025.
It is also shown, as an example, that the TS generation unit 2011 different from the aforementioned TS generation unit 2010 generates one program in a TS.
To be more specific, the TS generation unit 2011 includes an audio coding unit (shown as 20211) and a video coding unit (shown as 20221).
Moreover, the TS generation unit 2011 includes a packetization unit (shown as 20231 and 20232) for each of the audio and video service components in the program.
Furthermore, the TS generation unit 2011 includes a packetized-stream multiplexing unit 2024 and an L2 information processing unit 2025.
It is shown, as an example, that the physical layer processing unit 2012 generates two PLPs (that is, two pieces of PLP data).
To be more specific, the physical layer processing unit 2012 includes a PLP processing unit (shown as 20311 and 20312) for each of the PLPs.
It should be noted that, for convenience of explanation, the PLP data is referred to as the “PLP” when deemed appropriate in the present specification.
The physical layer processing unit 2012 includes a layer-1 (L1) information processing unit 2041, a frame structure unit 2051, and an OFDM signal generation unit 2061.
The following describes an operation performed by the transmitting apparatus 2000.
In each of the TS generation units 2010 and 2011, the corresponding audio coding unit (such as the units 20211 and 20212 of the TS generation unit 2010) performs audio source coding and the corresponding video coding unit (such as the units 20221 and 20222 of the TS generation unit 2010) performs video source coding.
As an example, source coding may be performed according to the H.264 standard.
Each of the packetization units (such as the units 20231 to 20234 of the TS generation unit 2010) packetizes an output from a function block corresponding to the current packetization unit.
Here, the corresponding function block refers to one of the audio coding units (20211 and 20212) and video coding units (20221 and 20222).
Each of the L2 information processing units 2025 of the TS generation units generates L2 information, such as program-specific information (PSI) and system information (SI).
Each of the packetized-stream multiplexing units 2024 of the TS generation units (the TS generation unit 2010, for example) multiplexes outputs from the packetization units (20231 to 20234) with an output from the L2 information processing unit 2025. As a result, the packetized-stream multiplexing unit 2024 generates a TS in which these outputs are multiplexed.
In the physical layer processing unit 2012, each of the PLP processing units (20311 and 20312) associates, with the PLP, the TS outputted from the TS generation unit (2010 or 2011) corresponding to the current PLP processing unit, and performs a process related to this PLP. Then, the PLP processing unit outputs mapping data (namely, a cell) concerning the PLP.
The L1 information processing unit 2041 performs a process related to the L1 information, and then outputs mapping data of the L1 information.
The frame structure unit 2051 generates a DVB-T2-based transmission frame as shown in FIG. 1 described above, using the mapping data of the PLP outputted from the PLP processing units and the mapping data of the L1 information outputted from the L1 information processing unit 2041. Then, the frame structure unit 2051 outputs the generated transmission frame.
The OFDM signal generation unit 2061 performs pilot signal insertion, inverse fast Fourier transform (IFFT), GI insertion, and P1 symbol insertion on the DVB-T2-based transmission frame structure outputted from the frame structure unit 2051. Then, the OFDM signal generation unit 2061 outputs a DVB-T2-based transmission signal.
Next, an operation performed by the PLP processing unit (20311 and 20312) is described in detail.
FIG. 3 is a diagram showing a configuration of a conventional DVB-T2-based PLP processing unit 2031N.
Each of the PLP processing units shown in FIG. 2 has the same configuration as the PLP processing unit 2031N.
As shown in FIG. 3, the PLP processing unit 2031N includes an input processing unit 2071, a forward error correction (FEC) coding unit 2072, a mapping unit 2073, and an interleaving unit 2074.
The input processing unit 2071 of the PLP processing unit 2031N transforms a TS packet to be sent to the PLP processing unit 2031N into a baseband frame.
The FEC coding unit 2072 performs Bose-Chaundhuri-Hocquenghem (BCH) coding and low-density parity-check (LDPC) coding and adds a parity bit, for each aforementioned baseband frame obtained as a result of the transform. Accordingly, the FEC coding unit 2072 generates an FEC frame.
The mapping unit 2073 performs mapping to I-Q coordinates, and then outputs mapping data (that is, a cell).
The interleaving unit 2074 sorts the mapping data (cells) within a time interleaving (TI) block including an integer number of FEC frames.
Next, an operation performed by the L1 information processing unit 2041 (shown in FIG. 2 and FIG. 4 that is described later) is explained in detail.
FIG. 4 is a diagram showing a configuration of a conventional DVB-T2-based L1 information processing unit 2041.
As shown in FIG. 4, the L1 information processing unit 2041 includes an L1 information generation unit 2081, an FEC coding unit 2082, a mapping unit 2083, and an interleaving unit 2084.
The L1 information generation unit 2081 of the L1 information processing unit 2041 generates transmission parameters, and transforms the generated transmission parameters into L1-pre information and L1-post information.
The FEC coding unit 2082 performs BCH coding and LDPC coding and adds a parity bit, for each of the aforementioned pieces of information (i.e., the L1-pre information and the L1-post information).
The mapping unit 2083 performs mapping to I-Q coordinates, and then outputs mapping data (that is, a cell).
The interleaving unit 2084 sorts the mapping data (cells) for each of the pieces of information (i.e., the L1-pre information and the L1-post information).
Here, Digital Video Broadcasting-Satellite Handheld (DVB-SH) is a standard for handheld/mobile receivers, based on hybrid satellite and terrestrial transmission. The DVB-SH standard defines two receiver classes, each of which has a different receiver.
A (receiver in) receiver class-1 can be implemented by a smaller amount of calculation and a smaller amount of memory, as compared with a (receiver in) receiver class-2.
The receiver class-2 is more robust to an extreme reception environment.
To be more specific, these two receiver classes are defined in view of a tradeoff between the amounts of calculation and memory and the reception performance (see Non Patent Literatures 3 and 4).
Moreover, Digital Video Broadcasting-Next Generation Handheld (DVB-NGH) is a transmission standard for handheld/mobile receivers. This standard defines, in Commercial Requirements, that “individual transmission quality for audio and video service components should be possible”. This indicates that transmission is performed using a PLP different for each of the service components (see Non Patent Literature 5).